1. Field of the Invention
Embodiments of the present invention generally relate to downhole tools and methods for using same. More particularly, embodiments of the present invention relate to a full bore flapper valve for a downhole tool and methods for using same.
2. Description of the Related Art
A wellbore typically penetrates multiple hydrocarbon bearing intervals, each requiring independent perforation and fracturing prior to being placed into production. Multiple plugs are often employed to isolate the individual hydrocarbon bearing intervals, thereby permitting the independent treatment of each interval with minimal impact to other intervals within the wellbore. This has been accomplished using one or more bridge plugs to isolate one or more lower intervals, thereby permitting the treatment of the one or more intervals above the plug. This process is repeated until all of the desired intervals have been treated. After treatment of each hydrocarbon bearing interval, the bridge plugs between the intervals are removed, typically by drilling and/or milling, permitting hydrocarbons to flow bi-directionally within the casing, preferably up-hole to the surface for recovery and collection. The repeated setting and removal of plugs within the wellbore is a time consuming and costly process that requiring multiple run-ins to place and remove the one or more downhole plugs and/or tools.
Plugs with check valves can eliminate the need to drill or mill conventional bridge plugs within the casing string, thereby minimizing the number of run-ins required and permitting more rapid production after perforating and fracing a hydrocarbon bearing interval. U.S. Pat. Nos. 4,427,071; 4,433,702; 4,531,587; 5,310,005; 6,196,261; 6,289,926; and 6,394,187 provide additional information on such plugs. Check valves, while minimizing run-in and run-out of tools into the casing string, have several drawbacks. First, the installation of check valves places one or more multi-piece assemblies downhole; these assemblies are prone to fouling by production fluids, potential mechanical failure due to damage from the passage of downhole tools, and/or chemical attack from routine wellbore operations. Second, the use of a check valve requires a complimentary valve seat disposed within the wellbore, proximate to the check valve. Constraints within the casing string often require the valve seat to have a smaller diameter or bore than the adjoining casing string, thereby limiting the passage of tools through the check valve and increasing the pressure drop through the tool.
There is a need, therefore, for a check-valve isolation tool permitting the isolation of one or more hydrocarbon bearing intervals, while minimizing the pressure drop through the tool and providing the maximum available open diameter for the passage of downhole tools.